This finally dropped for me just a few minutes ago. It was dropped by Doomscale Diabolist. In ZAM it says he's level 104. I'm level 105 and he conned red, so he's not level 104. At last when I fight him. It was an HA given by Marla Gaslow in Ethenere Tainted West. The mission was Marla #2: Seeking Refuge.

A little information on Doomscale Diabolist if you meet up with him. I parsed him and this version had 9.8 million hit points. He chain casts Petrifying Gaze which slows down spell casting greatly. It slows spell haste and attack speed by 80%. This fight lasted 374 seconds and my DPS was 26900. Considering how mind numbing slow my spells where this was ok. Clickies and AA's were not affected. What's odd in the other encounter my DPS was 39k. My spells were just as slow in that fight.

Doomscale Diabolist didn't really put up much of an offensive threat for a red conned named. During the duration of the fight I put up 2 aegis AA twice and used my lay of hands heal AA. I used the LOA AA at the end of the fight to prevent a spike of offense by the named, it really wasn't needed. At the beginning of the fight I used the AA's Heart OF Flame, Virulent Talon, Silent Casting,Frenzied Burnout, Improved Twin Cast,Intensity of the Resolute and the Fundament (First Spire of the Elements). I send in fluffy, servant and then the swarm. DeBuff with Malo and start my weave. I'll unleash the Servant of Ro when the pet swarm disapears. I watch my pets health,mana and merc's mana like a hawk. If the pet's health gets anywhere near 50% I'll use Companions Blessing and then Aegis of Kildrukaun.In this partcular fight the pet never went below 75% health. Any AA's I used were more preventive then anything.

Other than being a slow fight due to Petrifying Gaze it was pretty straight forward. I used the earth pet which held up well. I have EM 17 and a mana pool of 85k and 95k hit points after buffing. He had an anoying AE rampage which knocked me down to 45%, but the AE happened twice during the fight so it more of a nuisance than anything. The merc healed it right away.

Didn't they change the spawn frequency of CoTF heroic adventure named? So that the longer the adventure takes, the more likely a named is to spawn?
So Seeking Refuge is the least likely to spawn a named, since it is the fastest.

I'm 90% sure the devs did that a couple years ago. Does anyone remember for sure?